My ECT and oil temp sensors are failing. I replaced the ECT since that's the easy one to get to and the problem still exists -- so it looks like my problem is electrical.

The problem is also intermittent. Seems to happen under hard acceleration, which tells me there might be a loose ground or wire hitting *somewhere*. My ECT will go to "LOW" and then start reading "XXX". My oil temp will just read "LOW" the whole time and never go to "XXX".

When I checked voltage on both leads to the ECT sensor, I get ~5v clean on one side, and about 0.06v on the other when connected to the battery ground. When connected to a chassis ground the reading is a little lower but it's still not zero.

Because I'm reading voltage from a ground to another ground, does that mean I have a wiring problem somewhere? The red lead of my voltmeter was hooked up to the ground on the ECT sensor and the black lead was hooked up to the battery ground, so voltage was flowing FROM the ECT sensor harness to the battery at 0.06v.

Does the ECT and oil temp sensor share a common ground or fuse or anything? I am wondering why they both fail at the same time. I know a while ago my oil temp sensor was looking a little ratty (wiring sat too close to the headers a while back) so it may have found its way back to my LG's and is grounding out to them. I just don't have a lift to check this out yet.

Any other thoughts on how to track this problem down?

I am getting codes P1115 and P0118 which is consistent with electrical problems on the sensors.

 

Also, it's worth noting that if I run the red lead of my voltmeter straight to my battery ground, and then the black lead to the ground on the passenger frame rail near the front AC line port, I also get a voltage reading.

Not sure if that's normal -- could it indicate a ground fault somewhere around there?